### Home > INT3 > Chapter 10 > Lesson 10.2.2 > Problem10-135

10-135.

In a unit circle, if $\text{sin}(β) = –\frac { 4 } { 5 }$ and $π ≤ β ≤\frac { 3 \pi } { 2 }$, what are the exact values of $\text{cos}\left(β\right)$ and $\text{tan}\left(β\right)$?

Recall the trigonometric equations such as:
$\text{sin}^{2} β + \text{cos}^{2} β = 1$

$\text{cos}\beta=-\frac{3}{5},\text{tan}\beta=\frac{4}{3}$